Aaron Bernstein/Reuters
Homeland Security Secretary John Kelly says homegrown terrorist attacks are the most common, but he doesn't know how to stop them.

John Kelly, the man in charge of protecting the nation’s homeland security, admitted Sunday that he has absolutely no idea how to prevent homegrown terrorist attacks.

“There are so many aspects to this terrorist thing,” Kelly, secretary of the Department of Homeland Security, said on CBS’s “Face the Nation.”

“Obviously, you got the homegrown terrorists. I don’t know how to stop that. I don’t know how to detect that. You got other terrorist threats that come across the border.”

Kelly’s admission to CBS host John Dickerson was surprising, in part because of its candor. For all of President Donald Trump’s focus on the border and banning people from Muslim-majority countries from the United States, the administration apparently doesn’t know how to deal with what Kelly said are the most common types of attacks.

DICKERSON: I just want to follow up, Mr. Secretary. You said on the homegrown threat, a lot of people think that is the biggest threat. It was part of the San Bernardino shooting, a part of the Boston bombing. But you said you don’t know how to stop that. If that’s the biggest threat and you don’t know how to stop it, that seems like a big problem.

KELLY: It is a big problem. It is ― you know, depending on where you sit is where you stand on this, it is a big threat. Is it the number one threat? I think it’s the most common threat. ...

I think the appeal I would make on the homegrown threat is if you see something, say something. Whether you’re a parent, a sibling, an imam. And this extends frankly, John, to white supremacists and that kind of terrorism as well. If you see a young man or a young woman going down that path where they’re always on these kind of websites or saying things at church or in a mosque that are clearly disturbing, then tell someone about it so that we can help that kid, young man or woman, before they break the law.

In February, the Chicago Project on Security and Threats released a report looking at “the American face of ISIS” ― 104 individuals the Department of Justice indicted for ISIS-related crimes between March 2014 and August 2016, and eight individuals who died on behalf of ISIS either in a domestic attack or fighting in Syria.

The researchers found that these individuals were mostly born in the United States.

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As Kelly noted, cooperation with the communities these individuals belong to is key to fighting the terrorist threat. Trump, however, has alienated many potential allies by campaigning on a promise to implement a “Muslim ban.” A December 2015 press release from his campaign stated, “Donald J. Trump is calling for a total and complete shutdown of Muslims entering the United States until our country’s representatives can figure out what is going on.”

In January, Trump implemented the first version of his ban, taking aim at travelers and refugees from certain Muslim-majority nations. However, his order also had the effect of blocking and delaying green card holders who were trying to re-enter the United States.